Two-stroke cycle internal combustion engine



Oct. 20, 1 931. -.1. DA P TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE Filed June 25, 1927 Patented Oct. 20, 1931 UNITED 'STATES PATENT OFFICE JEAN DAP, OF PUI'EAUX, FRANCE, ASSIGNOR TO DAP-MOTOREZPATENTGESELLSCHAFT .M. B. 11., 0F COLOGNE-HO'LWEIDE, GERMANY TWQ-STROKE CYCLE INTERNAL COMBUSTION ENGINE Application fi1ed-Iune 25, 1927, Serial No.

This invention relates to a two-stroke cycle internal combustion engine of the kind wherein the combustible mixture is compressed in a separate compression cylinder and then transferred to the working cylinder when the working piston is near its inner dead centre.

According to the invention, to prepare the working cylinder for the admission of a combustible mixture compressed ready or practically ready for ignition, the burnt gases are drawn out of the cylinder so that the working piston returns in a vacuum. The compression piston drives the combustible mixture into the working cylinder without fall in pressure at the end of the compressionstroke, while afterwards the burnt mixture is removed as'completely as possible from the working cylinder by a suction device. The accompanying drawing is a diagram illustrative of the invention. Each system operating as a whole consists of two cylinders 1 and 2. The cylinder 1 is the working cylinder, the cylinder 2 the compression cylinder. Both cylinders are connected-together by'a pipe system. The compressed gas mixture can pass into this pipe system from the cylinder 2 through a valve 5, but its passage into the cylinder 1 is at first closed by a valve 6. In the pipe system is also a valve 8 which is an excess pressure valve adjustable to a desired pressure, while the valve 6 is positively operated by a cam 13 in such a manner that in known manner its lift can be varied from zero to a maximum. The pressure setting of the valve 8 is adjustable; by its aid the compression tpressure is regulated, while the charging o the working cylinder is regulated by the valve 6. After passing the valve 6 the mixture passes through the valve 7 into the working cylinder 1. This working cylinder 1 is constructed for the twostroke cycle, that is it has at its end the known exhaust ports 10 which are connected together by the manifold 11. In the usual twostroke cycle, scavenging is very deficient; the burnt gases are here therefore sucked out of the working cylinder by an ejector 12.

The ejector 12 is only shown as an example 201,516, and in Germany August 14, 1926.

inders, in which the air is then caught in the funnel of the ejector 12 and by stream action produces suction in the cylinder 1. In stationary engines, an ejector can also be used, formed in the usual manner, if other suction devices are not used. 1

The separation of the compression process from the actual working stroke and the evacuation of the burnt gases lowers the temperature in the Working cylinder and thus raises the volumetric efiiciency. The compression piston 4 acts in'advance of the working piston by an amount 0. The choice of this distance is controlled by two opposing factors; on one hand the compressor piston must force a sufficient volume of compressed gas mixtureinto the evacuated cylinder; on the other hand the ignition must be retarded for this period. The best amountof lead 0 must be determined by trial. Ad'vantageously the volume of the compression cylinde'r'is made so large that with rarified air.or air other- Wise deficient in oxygen, a sufiiciently large pression cylinder. The mechanism operating the valve 6 is in permanent connection with the driving members of the engine and consists for instance of the cam 13 and a lever 14. In order to vary the valve opening, the cam 13 for example may be slidable on its shaft and in known manner have a varying cross section so that the valve opening can be varied between zero and a maximum. In addition the valve 6 with its operating lever 14:, the inlet valve 7 and the electro-magnetic ignition device 15 serve another, double purpose. In thecircuit of the igniter is a contact device 29 in kinematic connection with the valve 6 or with its mechanical operating gear, which contact device only permits ignition when the valve 6 is quite closed. The

other purpose of the contact device 29 is to enable an exact ignition point to be conveniently set. This ignition point being once correctly set, ignition can be advanced or reoperated extra opening 20.

tarded in known manner by the electro-magnet-ic device 15. The co-action of the valves 6 and 7 prevents striking back of the flame in the working cylinder 1 into the parts containing combustion mixture. This arrangement works as follows. The valves 6 and 7 are both open during the transfer of gas from the compression cylinder 2 to the working cylinder 1. When the piston of the working cylinder has moved so far against the pressure that no further transfer of compressed mixture can take place, which occurs shortly before ignition, the valve 7 closes and an instant later the valve 6, which however only permits ignition after it is completely closed. This arrangement produces a very considerable reduction in fire risk.

It is obvious that in the case of where the exhausting device operated by the rotation of the engine, the engine cannot be started, since the working cylinder acts as a compressor, if its contents are not sucked OE, and

for this reason a de-compression device 1411 and 15a is provided, which can be constructed for example as follows. The cam 14a wh1ch is only coupled to the engine shaft when needed, operates a de-compression valve 28 through a cam rod 15a in such amanner-that the pressure in the cylinder is not great enough to prevent transfer of compression mixture and on the other hand closes sufficiently early to prevent escape of transferred mixture into the air. Such constructions are well known to those skilled in the art. The

gas mixture is made rich so that in spite of.

the dilution which occurs through mixing, certain ignition is ensured.

The upper part of the carbureter wh1ch 1s shown on a greatly enlarged scale for e'as1er comprehension, is connected with the pipe 23 through the excess pressure p1pe 24. The upper chamber 25 of the carbureter is closed by the adjustable excess pressure valve 8 which can be set for example b the lever 16. If with high pressure the va ve 8 opens, the mixture flows through the chamber 21 and in its expansion draws fuel out of the nozzle of the fuel pipe 31. The level of fuel in the pipe 31 is regulated in known manner by a float device 19; the quantity outflowing can be regulated by a valve 18. The mlxture drawn off from the chamber 26 through the pipe 22 can be very well regulated in itsair content, in the first dplace by the adwstable closure 17 and secon ly by the automatically Considerable variations can also be made by exchanging the cone 30. I

The general mode of operation of these individual parts is shortly as follows. At the.

end of the working stroke the burnt gases are i am the cylinder 1 towards the end of the stroke of I the piston 3 therein whereas during the other part of the stroke there was a reduced pressure or a very Sll%ht pressure arising from the burnt residues. xcess pressure is prevented by automatic opening of the valve 8, so that the combustible mixture after it has entirely passed into the cylinder 1 is i 'ted at a definite compression and drives forward the piston 3 which has in the meantime reversed its direction of motion. The returning compression piston 4 sucks in fresh combustible mixture, and if the excess pressure valve 8- has come into action, the-excess combustible mixture from the previous cycle, when the whole cycle recommences. e

What I claim is 1. In a two cycle internal combustion engine the combination of a Working cylinder, a suction device for evacuating said working cylinder, a pump cylinder timed with respect to said working cylinder, atransfer conduit, connecting said pump cylinder with said working cylinder, a carbureter, a suction conduit connecting said carbureter to said pump cylinder, a conduit conne'cting said transfer conduit to the inlet side of said carbureter, an adjustable valve in said connecting conduit opening to excess pressure in' said transfer conduit, and an engine actuated transfer valve in said transfer conduit timed to admit gas to said workin cylinder towards the end of itsworking stro e.

2. In a two cycle internal combustion engine the combination of a working cylinder, a suction device for evacuating said working cylinder, a pump cylinder timed with respect to said workin cylinder, a transfer conduit connecting said pump cylinder with said working cylinder, a carbureter, a suction conduit connecting said carbureter to said pump. cylinder, 'a conduit leading from said transfer conduit and terminating in a nozzle surrounding the fuel nozzle of said carbureter, an adjustable valve in said transfer conduit, and an engine actuated transfer valve in said transfer conduit timed to admit gas to said working cylinder towards the end of its working stroke.

3. In a two cycle internal combustion engine the combination of a working cylinder, a suction device for evacuating said working cylinder, a pump cylinder of greater dispersement than said working cylinder timed reter, an

with respect to said working cylinder, a transfer conduit connecting said pump cylinder with said working cylinder, a carbureter, a suction conduit connectin said carbureter to said pump cylinder, a con uit connectin said transfer conduit to the inlet sidelof sai carbureter, an adjustable valve in said connecting conduit opening to excess pressure in said transfer condult, and an engine actuated transfer valve in said transfer conduit timed to admit gas to said working cylinder towards the end of its working stroke.

4. In a two cycle internal a suction device for evacuating said working cylinder, a pump cylinder of greater dispersement than said working cylinder timed with cylinder, a transfer respect to said working ]i d pump Cy I1 er W1 conduit connecting sai said working cylmder, conduit connectlng said carbureter to said pump cylinder, a conduit leading'from said transfer conduit and terminating in a nozzle surroundingithefuel nozzle of said carbua gustable valve in said transfer conduit, an an engine actuated transfer valve in said transfer conduit timed to admit gas to said working cylinder towards the end of its working stroke.

. In testimony whereof I have signed my name to this specification.

JEAN DAP.

I combustion engine the combination of a working cylinder,

a carbureter, a suction 

